Radio frames in a Long Term Evolution (LTE) system include frame structures in a Frequency Division Duplex (FDD) mode and a Time Division Duplex (TDD) mode. As shown in FIG. 1, in a frame structure in the FDD mode, a 10 ms radio frame consists of 20 time slots which are 0.5 ms long and numbered as 0˜19, and time slots 2i and 2i+1 form a subframe i (herein, 0≤i≤9) with a length of 1 ms. As shown in FIG. 2, in a frame structure in the TDD mode, a 10 ms radio frame consists of two half frames with lengths of 5 ms, one half frame includes 5 subframes with lengths of 1 ms, and subframe i is defined into a combination of two time slots 2i and 2i+1 with lengths of 0.5 ms (herein, 0≤i≤9). An uplink and downlink configuration supported by each subframe is shown in Table 1, herein “D” represents a subframe dedicated to downlink transmission, “U” represents a subframe dedicated to uplink transmission, and “S” represents a special subframe configured for three domains, i.e. a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP) and an Uplink Pilot Time Slot (UpPTS).
TABLE 1Schematic Table for Uplink and Downlink Configuration Supported by Each SubframeDownlink-Uplink-uplinkdownlinkswitch Subframe number#configurationpoint period0123456789#0 5 msDSUUUDSUUU#1 5 msDSUUDDSUUD#2 5 msDSUDDDSUDD#310 msDSUUUDDDDD#410 msDSUUDDDDDD#510 msDSUDDDDDDD#6 5 msDSUUUDSUUD
From the above table, it can be seen that LTE TDD supports uplink and downlink switch periods of 5 ms and 10 ms. If a downlink-to-uplink switch point period is 5 ms, a special subframe may exist in two half frames; if the downlink-to-uplink switch point period is 10 ms, the special subframe only exists in the first half frame; subframe #0, subframe #5 and a DwPTS are always configured for downlink transmission; and an UpPTS and a subframe following a special subframe are dedicated to uplink transmission.
In an LTE FDD system, sending of a Physical Downlink Shared Channel (PDSCH) and corresponding Hybrid Automatic Repeat Request-Acknowledgement (HARQ-ACK) information in a downlink Hybrid Automatic Repeat Request (HARQ) is required to follow the following timing specification, that is, a timing relationship of the downlink HARQ is required to follow the following specification: when User Equipment (UE) detects transmission of a PDSCH or a Physical Downlink Control Channel (PDCCH) indicating downlink Semi-Persistent Scheduling (SPS) release in subframe n−4, the UE transmits corresponding HARQ-ACK information on uplink subframe n, that is, a feedback delay of the downlink HARQ is 4; and in a an LTE TDD system, a timing relationship of a downlink HARQ is required to follow the following specification: when UE detects transmission of a PDSCH or a PDCCH indicating downlink Semi-Persistent Scheduling SPS release in subframe n−k, the UE transmits corresponding HARQ-ACK information in uplink subframe n, herein k belongs to K, K is a {k0, k1, . . . , Km-1}, M is the total number of K, a maximum value of M is 4, a value corresponding to k is a feedback delay of the downlink HARQ, and values of K in different uplink and downlink configurations are shown in Table 2. From Table 2, it can be seen that the feedback delay of the downlink HARQ of the TDD system is more than or equal to the feedback delay 4 of the downlink HARQ of the LTE FDD system.
TABLE 2Downlink Related Group Index K: {k0, k1, . . . , Km−1} in TDD SystemUplink-downlinkSubframe number nconfiguration0123456789#0——6—4——6—4#1——7, 6 4———7, 6 4—#2——8, 7, ————8, 7, ——4, 6 4, 6 #3——7, 6, 116, 5 5, 4—————#4——12, 8, 6, 5, ——————7, 11 4, 7 #5——13, 12, 9, ———————8, 7, 5, 4, 11, 6#6——775——77—
In order to meet a requirement of the International Telecommunication Union-Advanced (ITU-Advanced), a Long Term Evolution Advanced (LTE-A) system, as an evolved standard of LTE, is required to support a larger system bandwidth (capable of maximally reaching 100 MHz), and is also required to be backwards compatible with an existing LTE standard. On the basis of an existing LTE system, a bandwidth of the LTE system may be combined to obtain a larger bandwidth, such a technology is called a Carrier Aggregation (CA) technology, and this technology can increase a spectrum utilization rate of an International Mobile Telecommunications-Advance (IMT-Advance) system, alleviate spectrum resource shortage and further optimize utilization of a spectrum resource.
In a system with Carrier Aggregation introduced, an aggregated carrier is called a Component Carrier (CC), and is also called a serving cell. Meanwhile, concepts of Primary Component Carrier/Cell (PCC/PCell) and Secondary Component Carrier/Cell (SCC/SCell) are also disclosed, and a system where Carrier Aggregation is performed at least includes a PCell and an SCell, herein the PCell is kept in an active state. In an existing Carrier Aggregation technology, FDD serving cell aggregation is supported, and a corresponding downlink HARQ feedback delay is 4. TDD serving cell aggregation under the same uplink and downlink configuration is supported, and TDD serving cell aggregation under different uplink and downlink configurations is also supported. For TDD serving cell aggregation, a corresponding downlink HARQ feedback delay is k, and a value of k is shown in Table 2. In terms of feedback delay, a feedback delay of an existing Carrier Aggregation TDD system is more than or equal to that of a Carrier Aggregation FDD system.
For the problem that a feedback delay of a Carrier Aggregation TDD system is more than or equal to that of a Carrier Aggregation FDD system in a related technology, there has been no effective solution yet.